It is a reoccurring problem in the use of nuts and bolts that the nut becomes frozen on the shank of the bolt. This generally results from the fact that the portion of the bolt which extends beyond the nut is coated with paint or, if not, rusts. Also, this exposed shank portion can be nicked or bumped marring the threads. Then, when it is time to remove the nut, as the nut moves axially off the shank, the paint and rust particles build up between the mating threads increasing the rotational torque necessary for removal to a point where removal without damaging the threads becomes impossible. Or, in the case of marred threads, the nut cannot be removed unless new threads are cut.
This problem can be even greater with a double-ended stud. In one such application, one end of the stud has a self-tapping thread form which is received in a comparatively soft material such as plastic. A nut attaches the stud to a base member which may be a layer of sheet metal. The entire assembly is then coated with paint. It is generally necessary to loosen the nuts to effect adjustment of the plastic layer with respect to the sheet metal. As the nut is removed, again, the paint and marred thread act to increase the resistance to removal. If the nut locks on the second threaded shank, the double-ended stud will rotate with the nut causing it to rotate out of the plastic. Proper re-seating of the fastener is difficult and, it may not be possible to firmly reseat the stud.
The present invention eliminates such unwanted locking of threads between a nut and bolt. The threads nearest the terminal end and, in fact, all threads projecting beyond the surface of the nut, have a thread crest diameter which is less than that of the threads which mate with the nut. The thread crest height in this region is still sufficient to engage with the internal threads of the nut but, is sufficiently reduced to provide adequate clearance for paint and rust particles as well as provide room to clear marred threads.
The features, advantages and objects of the present invention will be more fully understood following a reading of the following specification when taken in conjunction with the accompanying drawings.